slipstream444

[attachment=34117:S2000 UAO ZRT-1.jpg][attachment=34116:S2000 UAO ZRT.jpg]

slipstream444

The first sample was Amsoil ATM 10W30, OEM PCX filter and I was still running the oiled foam filter in my Comptech intake.
I believe the slightly elevated contamination (silicon) in the oil was due to a completely worn out Comptech air filter, and this likely skewed the results for this sample.


The 2nd and 3rd samples were Amsoil ZRT, OEM PCX filter and I switched to an aFe filter in my Comptech intake. There was less contamination in these samples.

The first ZRT sample was improperly listed as ATM - hence the yellow highlight by the lab for the Calcium and Phosphorous numbers (out of spec for ATM).

You can see the ZRT has almost twice the Zinc and Phosphorous as the ATM. The ATM has almost 4 times as much Molybdenum and about 1000ppm higher Calcium content though.

I switched to the ZRT due to the fact it has a lower NOAK volatility rating, it has a lot of ZDDP, it is a little cheaper per quart than ATM - and it is still a solid synthetic 10W30. The biggest consideration was the ZDDP content in order to provide a little more protection for my thrust washers - considering I am running an ACT pressure plate, which has a lot more thrust load on the crank. Strangely enough, my car burns a little more ZRT than ATM. It's still very low consumption - a little over 0.30 US QT in 3,000 miles versus less than 0.20 US QT per 3,000 miles.

The ZRT is not designed for much more than a 3,000 mile change interval. This was also not a problem for me because I have pretty much stuck to 3,000 mile interval (or so) even though I have run ATM since the engine was broken in (a 25,000 mile oil).

ZRT is a litte higher in viscosity than ATM as well. ATM in fact could actually get away with being sold as a 5W30.

zeroptzero

Thanks for posting, I always wanted to try their Z-Rod formula, too bad they lowered the moly and boron, that would have been a nice combo with the added phos and zinc.

SpitfireS

Thanks for posting the UOA

You mention the thrust bearing.
The best way to protect it IMO - when using a stronger PP - is to not start with the clutch in.
IOW: disable the switch.
And don't keep the clutch pressed in for (a) minute(s) waiting for the lights to go green and staying in gear.
You won't beat the automatic transmission guys anyway

In a running engine I think the thrust bearing is fed with semi-pressurized oil coming out of the crank main that is next to it.
I don't think it really needs extra protection from ZDDP but it also doesn't hurt.
That said: using the type of oil you mention "hurts" long drain intervals - and not just a little.

Looking at the specs of the ZRT I see the HTHS is pretty high for a 30 weight (nice!) compared with AZO for example.
But what I don't understand is why the Four-Ball Wear Test (ASTM D-4172) is worse for the ZRT, again, compared with AZO.
So what is the ZDDP doing?
Sure, we could start a multi page discussion on the validity of the ASTM D-4172 test performed on engine oils.
I'm not syaing just because of one (1) test an oil is worse or better than the other.
Wouldn't one expect the oil that's recommended to protect flat tapped engines do better in this test than a "thin" 0W-30 though?

I'm sure ATM sales would drop if it was labelled 5W-30 as that stuff is way.. and I mean WAY!! too thin to protect an engine!
And if the manual says 10W-30 that's what I will put in, plain and simple, a no brainer.
(people that think like this actually have a no-brain when it comes to engine oil, but you'll never get them to understand, no matter what you say)

zeroptzero

Like mentioned above the best thing you can do for the thrust bearings is to modify the car so the clutch doesn't have to be used on start-up. I screwed an acorn nut on the threaded end of the clutch switch to keep the switch pin engaged so the clutch does not have to be pushed in to start the car. I have the switch zip tied and off to the side of the original mounting location so it can be reversed easily if needed.

I find the 4-ball wear test results that Amsoil reports for their different oils can be confusing, not always what you might expect. I'm not sure if the 4-ball test means anything when it comes to motor oil.

slipstream444

I agree that starting the car with the clutch out is the best way to avoid excessive thrust washer wear. I posted a DIY to bypass the clutch interlock switch a few years back to facilitate this. Nevertheless, I am always looking at ways to better protect my car's engine.

https://www.s2ki.com/...-switch-bypass/

As for the Four Ball test: Amsoil ATM and AZO have a Four Ball test result of 0.35 versus a 0.36 for the ZRT. I don't think you can argue there is really a difference between a 0.35mm and a 0.36mm scar - not from a statistically significant or practical standpoint at least. I'm pretty convinced if you ran the same test 10 times you would see the results would average out to be the same. I would argue the HTHS results are a much more significant measurement to consider. The ZRT has a 3.6 versus a 3.1 for AZO and 3.2 for ATM.

slipstream444

The question I would pose to someone in the know like BirdShot is: which formulation is better... higher Molybdenum or higher Zinc/Phosphorous content? Obviously the lower ZDDP numbers are easier on the catalyst, but is that combo better for lower wear in comparison to an oil like ATM (for example)? I agree the viscosity of ATM is slightly better overall in comparison to ZRT - being ATM is more akin to a 5W30 than a 10W30 (even though it is sold as a 10W30). I'll likely stay with ZRT for a while and see how it trends over time. Both oils return a good UOA - especially considering how hard I drive my car.

Additionally, I conducted another leak down at 75K and the leak down numbers were all still lower than 2% on all cylinders, and the difference between cylinders was barely measurable. I don't expect that wear trend to change with continued use of ZRT. Time will tell.